This invention relates to ion cyclotron resonance mass spectrometers.
Ion cyclotron resonance mass spectrometers (ICR mass spectrometers) are known in which trapping potentials are applied to oppositely located electrodes of an analyzer cell to trap ions which are rotated by a magnetic field applied across the cell. Resonance is established for different ions based on their charge/molecular weight ratio by applying an alternating electric field across the cell to impart kinetic energy to those ions resonant with the alternating field. The ions which are in resonance may be sensed by marginal oscillators, electroscopes, broad band balanced bridge means, or the like. These ion cyclotron resonance mass spectrometers operate in a high vacuum such as 10.sup.-7 torr.
In some ICR spectrometers, one-region analyzer cells are used, which have the source, analyzer and detector in the same region to perform their functions sequentially in time without changing location rather than being based on a sequence that occurs as the ions move to spatially separated locations, as in drift type analyzer cells.
In a prior art type of one-region ICR spectrometer such as that disclosed in U.S. Pat. No. 3,742,212 issued June 26, 1973, to McIver and U.S. Pat. No. 4,105,917 issued Aug. 8, 1978, to McIver and Ledford, the molecules of the sample are pulled from the analyzer cell by the fast pump that evacuates the main vacuum housing in which the one-region analyzer cell is mounted.
The prior art ion cyclotron resonance mass spectrometers have a disadvantage in that only a small portion of the sample is available for analysis, the remainder being drawn from the system without entering the analyzer cell or being too quickly removed from the analyzer cell by the vacuum pump.